package DataStuctures.Map;


public class BSTMap<K extends Comparable<K>,V> implements Map<K,V> {

    private class Node{
        public K key;
        public V value;
        public Node left,right;

        public Node(K key,V value) {
            this.key = key;
            this.value = value;
            left = null;
            right = null;
        }
    }

    private Node root;
    private int size;

    public BSTMap() {
        root = null;
        size = 0;
    }

    @Override
    public void add(K key, V value) {

        root = add(root,key,value);

    }

    private Node add(Node node, K key, V value) {

        if (node == null) {
            size ++;
            return new Node(key,value);
        }

        //大于为正 小于为负
        if (key.compareTo(node.key) < 0) {
            node.left = add(node.left,key,value);
        }else if(key.compareTo(node.key) > 0) {
            node.right = add(node.right,key,value);
        }else {
            node.value = value;
        }
        return node;

    }

    private Node getNode(Node node,K key){
        if (node == null) {
            return null;
        }

        if (key.compareTo(node.key) == 0) {
            return node;
        } else if (key.compareTo(node.key) < 0) {
            return getNode(node.left,key);
        }else {
            return getNode(node.right,key);
        }

    }

    @Override
    public V remove(K key) {
        Node node = getNode(root, key);
        if (node !=null) {
            root = remove(root,key);
            return node.value;
        }
        return null;
    }

    private Node remove(Node node, K key) {


        if( node == null )
            return null;

        if( key.compareTo(node.key) < 0 ){      //如果比当前节点的值要小，继续往左递归，直到找到=0的元素
            node.left = remove(node.left , key);
            return node;
        }
        else if(key.compareTo(node.key) > 0 ){  //如果比当前节点的值要大，继续往右递归，直到找到=0的元素
            node.right = remove(node.right, key);
            return node;
        }
        else{   // e.compareTo(node.e) == 0

            // 待删除节点左子树为空的情况    ——>跟叶子节点的情况是一致的，无需单独处理
            if(node.left == null){
                Node rightNode = node.right;
                node.right = null;
                size --;
                return rightNode;
            }

            // 待删除节点右子树为空的情况
            if(node.right == null){
                Node leftNode = node.left;
                node.left = null;
                size --;
                return leftNode;
            }

            //最复杂的二叉树删除
            // 待删除节点左右子树均不为空的情况

            // 找到比待删除节点大的最小节点, 即待删除节点右子树的最小节点
            // 用这个节点顶替待删除节点的位置   successor后继
            Node successor = minimum(node.right);   //找到当前节点的后继
            size ++;

            successor.right = removeMin(node.right);
            successor.left = node.left;

            node.left = node.right = null;
            size --;

            return successor;
        }
    }


    public V removeMin(){
        V ret = minimum();
        root = removeMin(root);
        return ret;
    }

    //删掉以node为根的二分搜索树中的最小节点
    //返回删除节点后新的二分搜索树的根
    private Node removeMin(Node node) {
        if(node.left == null){
            Node rightNode = node.right;
            node.right = null;
            size --;
            return rightNode;
        }
        node.left = removeMin(node.left);
        return node;
    }


    public V minimum(){
        if(size == 0 ){
            throw new IllegalArgumentException("BST is empty");
        }

        Node minNode = minimum(root);
        return minNode.value;
    }

    //返回以node为根的二分搜索树的最小值所在的节点
    private Node minimum(Node node) {
        if(node.left == null){
            return node;
        }
        return minimum(node.left);
    }

    @Override
    public boolean contains(K key) {
        return getNode(root,key)!=null;
    }

    @Override
    public V get(K key) {
        Node node = getNode(root, key);
        return node == null? null : node.value;
    }

    @Override
    public void set(K key, V newValue) {
        Node node = getNode(root, key);
        if (node == null) {
            throw new IllegalArgumentException(key +" doesn't exist!");
        }
        node.value = newValue;
    }

    @Override
    public int getSize() {
        return size;
    }

    @Override
    public boolean isEmpty() {
        return size == 0;
    }
}
